Many people suffer from diabetes. Because of their diabetes, many of these people have to inject several times a day, normally after taking food, and therefore need to carry insulin syringes around with them wherever they go. There are presently a number of different designs of insulin syringes of greater or lesser sophistication with which the dose, i.e. the number of units to be injected, can be set, and which accommodate insulin for several dosages.
A problem with such insulin syringes is that, although there are some models having the shape of a large pen or the like, they can in some circumstances be too awkward to carry around. In the summer, for example, when people wear fewer clothes, for example at the beach or the like, it is a problem always having to carry around a syringe shaped like a pen. Nor is it particularly convenient to carry it around in trouser pockets, as it can press against the skin, for example when sitting down or the like. This means that in such cases the insulin is not taken regularly, nor is it taken as often as may be required, thus increasing the risk of other diseases, for example liver diseases. Moreover, they do not always give an exact dose. Instead, the dose obtained may vary from a given metered dose quantity.
A more exact dose is provided by conventional syringes with an axially extending plunger that moves to and fro and is designed such that, when drawn out, it sucks liquid through the needle to the space and, when pressed in, discharges liquid from the space through the injection needle, but they are difficult to use on oneself and are also difficult to carry around on one's person.